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tccrab · 10-22-2006

Turn ignition switch to "Off".
Ground ALDL terminal "B" to ground ("A").
Consult the manual pg. 6E-6 for picture of ALDL connector.
Turn ignition switch "On".
The "Service Engine Soon" light should flash Code 12 three (3) times,
followed by any other codes (in numerical order from lowest to highest), which may be stored.
Each code will flash three (3) times.
After all the codes are displayed, the sequence starts over with "12" again.

ZR1 ECM CODES 1990 TO 1992:

Code #12: Normal No Codes.
Code #13: Left Oxygen Sensor Circuit.
Code #14: Coolant Temperature Sensor Circuit High.
Code #15: Coolant Temperature Sensor Circuit Low.
Code #16: Direct Ignition System (DIS) Fault Line Circuit
Code #21: Throttle Position Sensor Circuit High.
Code #22: Throttle Position Sensor Circuit Low.
Code #23: Manifold Air Temperature Sensor Circuit Low.
Code #24: Vehicle Speed Sensor Circuit.
Code #25: Manifold Air Temperature Sensor Circuit High.
Code #31: Camshaft Sensor Circuit.
Code #33: Manifold Absolute Pressure Sensor Circuit High - Low Vacuum.
Code #34: Manifold Absolute Pressure Sensor Circuit Low - High Vacuum.
Code #36: Direct Ignition System (DIS) Circuit (missing or extra EST signal)
Code #41: Cylinder Select Error (Faulty or Incorrect Mem-Cal)
Code #42: Electronic Spark Timing (EST) Circuit.
Code# 43: Electronic Spark Control (ESC) Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #45: Left Oxygen Sensor Circuit Rich.
Code #46: Vehicle Anti-Theft System (VATS)(PASS-Key) Circuit.
Code #51: Mem-Cal Error.
Code #52: Engine Oil Temperature Sensor Circuit Low.
Code #53: System Voltage.
Code #54: Fuel Pump Circuit (Low Voltage)
Code #55: System Voltage
Code #56: Vacuum Sensor Circuit.
Code #61: Secondary Port Throttle Valve System.
Code #62: Engine Oil Temperature Sensor Circuit High.
Code #63: Right Oxygen Sensor Circuit Open.
Code #64: Right Oxygen Sensor Circuit Lean.
Code #65: Right Oxygen Sensor Circuit Rich.

The above codes are specific for the ZR1's (Vin J). Page 6E3-A-1 1990 Helms Service Manual

TomC
'90ZR1 #792

10-22-2006	#4
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,663	Re: Runs really bad at idle! Turn ignition switch to "Off". Ground ALDL terminal "B" to ground ("A"). Consult the manual pg. 6E-6 for picture of ALDL connector. Turn ignition switch "On". The "Service Engine Soon" light should flash Code 12 three (3) times, followed by any other codes (in numerical order from lowest to highest), which may be stored. Each code will flash three (3) times. After all the codes are displayed, the sequence starts over with "12" again. ZR1 ECM CODES 1990 TO 1992: Code #12: Normal No Codes. Code #13: Left Oxygen Sensor Circuit. Code #14: Coolant Temperature Sensor Circuit High. Code #15: Coolant Temperature Sensor Circuit Low. Code #16: Direct Ignition System (DIS) Fault Line Circuit Code #21: Throttle Position Sensor Circuit High. Code #22: Throttle Position Sensor Circuit Low. Code #23: Manifold Air Temperature Sensor Circuit Low. Code #24: Vehicle Speed Sensor Circuit. Code #25: Manifold Air Temperature Sensor Circuit High. Code #31: Camshaft Sensor Circuit. Code #33: Manifold Absolute Pressure Sensor Circuit High - Low Vacuum. Code #34: Manifold Absolute Pressure Sensor Circuit Low - High Vacuum. Code #36: Direct Ignition System (DIS) Circuit (missing or extra EST signal) Code #41: Cylinder Select Error (Faulty or Incorrect Mem-Cal) Code #42: Electronic Spark Timing (EST) Circuit. Code# 43: Electronic Spark Control (ESC) Circuit. Code #44: Left Oxygen Sensor Circuit Lean. Code #45: Left Oxygen Sensor Circuit Rich. Code #46: Vehicle Anti-Theft System (VATS)(PASS-Key) Circuit. Code #51: Mem-Cal Error. Code #52: Engine Oil Temperature Sensor Circuit Low. Code #53: System Voltage. Code #54: Fuel Pump Circuit (Low Voltage) Code #55: System Voltage Code #56: Vacuum Sensor Circuit. Code #61: Secondary Port Throttle Valve System. Code #62: Engine Oil Temperature Sensor Circuit High. Code #63: Right Oxygen Sensor Circuit Open. Code #64: Right Oxygen Sensor Circuit Lean. Code #65: Right Oxygen Sensor Circuit Rich. The above codes are specific for the ZR1's (Vin J). Page 6E3-A-1 1990 Helms Service Manual TomC '90ZR1 #792 Last edited by tccrab; 10-23-2006 at 01:23 AM.